Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$49.83	8.711%	$54.1707	$54.17	$54.15	$54.20
Purchase #2	$231.68	13.113%	$262.0602	$262.06	$262.05	$262.10
Purchase #3	$88.67	12.211%	$99.4975	$99.50	$99.50	$99.50
Purchase #4	$203.54	11.251%	$226.4403	$226.44	$226.45	$226.40
Purchase #5	$247.89	3.808%	$257.3297	$257.33	$257.35	$257.30
Purchase #6	$72.62	13.210%	$82.2131	$82.21	$82.20	$82.20
Purchase #7	$69.37	4.251%	$72.3189	$72.32	$72.30	$72.30
7 purchase totals =	$963.60		$1,054.0304	$1,054.03	$1,054.00	$1,054.00